A single-crystal lithium-rich manganese-based cathode material and its preparation method

Abstract

This invention belongs to the technical field of cathode materials for secondary batteries. More specifically, it relates to a single-crystal lithium-rich manganese-based cathode material and its preparation method. The specific preparation steps of this invention include: mixing the precursor, LiOH·2H2O, and H3BO3 in a molar ratio of 1:1.05:0.02, followed by wet ball milling to obtain ball milling material; calcining the ball milling material at 500-550℃ for 3-5 hours, then further heating to 850-880℃ and calcining for 8-10 hours, followed by cooling, discharge, and sieving to obtain primary sintered material; mixing the primary sintered material with anhydrous ethanol in a mass ratio of (4-5):1, followed by wet sand milling for 50-60 minutes, and freeze-drying to obtain sand milling material with a D50 of 1-2 μm; mixing the sand milling material with lithium carbonate in a mass ratio of 1:0.02-0.025, heating to 1000-1050℃ in an air atmosphere, sintering for 12-15 hours, cooling, and discharging to obtain single-crystal lithium-rich manganese-based cathode material.

Description

Technical Field

[0001] This invention belongs to the technical field of cathode materials for secondary batteries. More specifically, it relates to a single-crystal lithium-rich manganese-based cathode material and its preparation method. Background Technology

[0002] Compared to polycrystalline ternary materials, monocrystalline ternary materials exhibit improved voltage resistance. The charging cutoff voltage for conventional polycrystalline materials is 4.2V, while monocrystalline ternary materials can reach 4.45V. Similarly, monocrystalline lithium-rich manganese-based materials demonstrate higher high-voltage resistance than polycrystalline lithium-rich materials. Conventional polycrystalline lithium-rich materials can cycle up to approximately 1000 times at 4.5V, but their cycle stability significantly decreases at higher voltages, such as 4.8V. To improve the stability of lithium-rich materials, it is necessary to develop them towards monocrystalline structures. However, monocrystalline lithium-rich materials generally struggle to maintain a high capacity while preserving their monocrystalline morphology. Currently, most lithium-rich monocrystalline materials are quasi-monocrystalline materials, and their capacity falls short of ideal requirements. Summary of the Invention

[0003] The technical problem this invention aims to solve is the poor size and morphological uniformity of single-crystal lithium-rich manganese-based cathode materials obtained by existing preparation methods. For example, since conventional precursors are themselves secondary spherical particles, well-dispersed single-crystal particles cannot be obtained through conventional sintering methods, thus affecting the material's capacity. Based on the above difficulties, this invention provides a single-crystal lithium-rich manganese-based cathode material and its preparation method.

[0004] The purpose of this invention is to provide a method for preparing a single-crystal lithium-rich manganese-based cathode material.

[0005] Another objective of this invention is to provide a single-crystal lithium-rich manganese-based cathode material.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a single-crystal lithium-rich manganese-based cathode material, the specific preparation steps of which include:

[0008] One-time sintering:

[0009] The precursor, LiOH·2H2O, and H3BO3 were mixed in a molar ratio of 1:1.05:0.02 and then wet-milled to obtain the ball milling material.

[0010] The precursor has the molecular formula: Ni 0.13 Co 0.13 Mn 0.54 (OH)2;

[0011] After calcining the ball mill at 500-550℃ for 3-5 hours, the temperature is further increased to 850-880℃ and calcined for 8-10 hours. After cooling, the material is discharged, sieved, and the primary sintered material is obtained.

[0012] Material discreteness:

[0013] After mixing the primary sintering material with anhydrous ethanol at a mass ratio of (4-5):1, the mixture is wet-milled for 50-60 minutes and then freeze-dried to obtain abrasive material with a D50 of 1-2 μm.

[0014] Secondary sintering:

[0015] After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.02-0.025, the mixture is heated to 1000-1050℃ in air and sintered for 12-15 hours. After cooling, the material is discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

[0016] The beneficial effects of the above technical solution are as follows:

[0017] The above technical solution employs wet sand milling and freeze drying after the first sintering to disperse the material, and then performs a further second sintering. The advantage of this is that the inventors discovered during the preparation process that soft agglomerates exist between the particles after the first sintering. If the second sintering is performed directly or the sintering is completed in one go, it will lead to uneven crystal growth during the second sintering. The sand milling process can mechanically separate the soft agglomerates, and the freeze drying process also avoids the possibility of the particles re-agglomerating during the drying process. This ensures the dispersion of the particles after the first sintering and provides a guarantee for the consistency of the single crystal morphology and size of the particles in the final second sintering.

[0018] In addition, the inventors discovered that by adding boric acid during a single sintering process, abnormal grain growth can be suppressed, thus preventing polycrystalline agglomeration.

[0019] Furthermore, the specific preparation steps of the precursor include:

[0020] The precursor was obtained by co-precipitation:

[0021] A composite metal salt solution was prepared with a Ni:Co:Mn molar ratio of 0.13:0.13:0.54.

[0022] A mixed solution of sodium hydroxide and ammonia was used as the precipitant.

[0023] First, add bottom water to the reactor. The volume of bottom water should be 0.2-0.3 times the volume of the compound metal salt solution. Adjust the pH of the bottom water to 10.8-11.2 using ammonia.

[0024] Under stirring, nitrogen was used as a protective gas. Then, a compound metal salt solution was added dropwise to the reactor at a uniform rate, and a precipitant was added dropwise at the same time to control the pH of the material in the reactor to be maintained at 10.8-11.2. After the addition was completed, the reaction was stirred for 8-12 hours.

[0025] The precursor is obtained by filtration, washing, and drying.

[0026] The beneficial effects of the above technical solution are as follows:

[0027] The inventors discovered in their research that the synergistic effect of sodium hydroxide and ammonia in the co-precipitation process of precursors can regulate the size and morphology of precursor particles, thereby indirectly affecting the single-crystal morphology of the final product. However, if the precipitant is directly added to the metal salt solution, it will lead to rapid local precipitation, thus affecting the dispersibility and size uniformity. By using a bottom water solution and adding ammonia as a complexing agent to the bottom water to buffer the influence of sodium hydroxide, the main component of the precipitant, this problem can be significantly improved.

[0028] Furthermore, the wet ball milling includes:

[0029] Add the material to the ball mill jar, and add anhydrous ethanol at 30-40% of the mass of the precursor. Then add zirconia ball milling beads with a diameter of 0.3 mm, and ball mill and mix for 80-120 min at a speed of 300-400 r / min.

[0030] Furthermore, the primary sintering also includes:

[0031] In an air atmosphere, the ball mill material is heated to 500-550℃ at a heating rate of 2-4℃ / min, and then held at that temperature for 3-5 hours. After that, the temperature is further increased to 850-880℃ at a heating rate of 6-8℃ / min, and then held at that temperature for 8-10 hours. After cooling, the material is discharged, sieved, and the primary sintered material is obtained.

[0032] The beneficial effects of the above technical solution are as follows:

[0033] In a single sintering process, a low heating rate is first used to raise the temperature to the corresponding temperature. This can prevent the rapid escape of moisture from causing the precursor particles to burst. In addition, since boric acid begins to melt at around 170°C and decomposes into boron oxide above 300°C, a slow heating rate can make it more evenly distributed on the surface of the precursor particles, avoiding uneven particle size or morphology caused by local sintering over-sintering.

[0034] Based on this, a faster heating rate is used when heating to higher temperatures. This is mainly because, at higher temperatures, oxides begin to undergo solid-state reactions to form layered crystal structures. Rapid heating can prevent abnormal grain growth and avoid over-sintering of some particles.

[0035] Furthermore, the material discretization also includes:

[0036] The sintered material was mixed with anhydrous ethanol at a mass ratio of (4-5):1 and then added to a planetary sand mill. Zirconia grinding beads with a diameter of 0.3 mm were added. The mixture was wet-milled for 50-60 minutes at a speed of 900-1000 r / min. During the sand milling process, the material temperature was controlled to not exceed 30℃ by circulating water cooling. After the sand milling was completed, the mixture was freeze-dried to obtain abrasive material with a D50 of 1-2 μm.

[0037] Furthermore, the freeze-drying includes:

[0038] After being rapidly frozen at -80℃ for 2 hours, the sample was then freeze-dried under vacuum at a vacuum level of 0.1 mbar for 24 hours.

[0039] Furthermore, the secondary sintering also includes:

[0040] After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.02-0.025, air is introduced at a rate of 0.2-0.3 L / min, and the mixture is heated to 1000-1050℃ at a rate of 5-7℃ / min in the air atmosphere. After sintering at this temperature for 12-15 hours, the mixture is rapidly cooled to room temperature at a rate of 10-12℃ / min and discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

[0041] The beneficial effects of the above technical solution are as follows:

[0042] After secondary sintering, a rapid cooling rate is used. This is mainly because, under high temperature conditions, grains continue to grow through solid-phase diffusion. Rapid cooling can quickly terminate this process, preventing the grain size distribution from becoming too fast. More importantly, a rapid cooling rate can lock in a uniform atomic arrangement during sintering, preventing the segregation of transition metals in the lattice caused by a slower cooling rate.

[0043] Furthermore, in the precipitant, the concentration of sodium hydroxide is 4.0-4.2 mol / L, and the concentration of ammonia is 0.5-0.6 mol / L.

[0044] Furthermore, the co-precipitation to obtain the precursor also includes:

[0045] Under stirring conditions at a speed of 600-800 r / min and a temperature of 48-52℃, with nitrogen as the protective gas, a compound metal salt solution is added dropwise to the reactor at a rate of 40-50 mL / min, while a precipitant is added dropwise to adjust the pH of the material in the reactor to be maintained at 10.8-11.2. After the addition is completed, the reaction is stirred for 8-12 hours.

[0046] A single-crystal lithium-rich manganese-based cathode material is prepared by the above-described preparation method. Attached image description:

[0047] Figure 1 This is a SEM image of the product in Embodiment 1 of the present invention;

[0048] Figure 2 This is a SEM image of the product in Comparative Example 1 of this invention. Detailed Implementation

[0049] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0050] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0051] Example 1

[0052] The precursor was obtained by co-precipitation:

[0053] A compound metal salt solution was prepared using nickel sulfate, cobalt sulfate, and manganese sulfate as metal salt raw materials, with a Ni:Co:Mn molar ratio of 0.13:0.13:0.54.

[0054] A mixed solution of sodium hydroxide and ammonia was used as the precipitant.

[0055] The precipitant contains sodium hydroxide at a concentration of 4.0 mol / L and ammonia at a concentration of 0.5 mol / L.

[0056] First, add bottom water to the reactor. The volume of bottom water is 0.2 times the volume of the compound metal salt solution. Adjust the pH of the bottom water to 10.8 using ammonia water. Use deionized water as the bottom water.

[0057] Under stirring conditions at a speed of 600 r / min and a temperature of 48℃, with nitrogen as the protective gas, a compound metal salt solution was added dropwise to the reactor at a rate of 40 mL / min, while a precipitant was added dropwise to maintain the pH of the material in the reactor at 10.8. After the addition was completed, the reaction was stirred for another 8 hours.

[0058] Filtration, washing and drying yield the precursor;

[0059] One-time sintering:

[0060] The precursor, LiOH·2H2O, and H3BO3 were mixed in a molar ratio of 1:1.05:0.02, and then added to a ball mill jar. Anhydrous ethanol (30% of the precursor mass) was added, followed by zirconia grinding beads with a diameter of 0.3 mm. The mixture was then wet-milled for 80 min at a speed of 300 r / min to obtain the ball milling material.

[0061] The precursor has the molecular formula: Ni 0.13 Co 0.13 Mn 0.54 (OH)2;

[0062] In an air atmosphere, the ball mill material was heated to 500°C at a heating rate of 2°C / min, held at that temperature for 3 hours, and then heated to 850°C at a rate of 6°C / min for 8 hours. After cooling, the material was discharged, sieved, and the primary sintered material was obtained.

[0063] Material discreteness:

[0064] The primary sintered material was mixed with anhydrous ethanol at a mass ratio of 4:1 and then added to a planetary sand mill. Zirconia grinding beads with a diameter of 0.3 mm were also added. The mixture was wet-milled for 50 min at a speed of 900 r / min. During the sand milling process, the material temperature was controlled to not exceed 30℃ by circulating water cooling. After the sand milling was completed, the mixture was rapidly frozen at a temperature of -80℃ for 2 h and then vacuum freeze-dried at a vacuum degree of 0.1 mbar for 24 h to obtain abrasive material with a D50 of 1 μm.

[0065] Secondary sintering:

[0066] After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.02, air is introduced at a rate of 0.2 L / min, and the mixture is heated to 1000 °C at a rate of 5 °C / min in the air atmosphere. After sintering at this temperature for 12 h, the mixture is rapidly cooled to room temperature at a rate of 10 °C / min and discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

[0067] Example 2

[0068] The precursor was obtained by co-precipitation:

[0069] A compound metal salt solution was prepared using nickel sulfate, cobalt sulfate, and manganese sulfate as metal salt raw materials, with a Ni:Co:Mn molar ratio of 0.13:0.13:0.54.

[0070] A mixed solution of sodium hydroxide and ammonia was used as the precipitant.

[0071] The precipitant contains sodium hydroxide at a concentration of 4.1 mol / L and ammonia at a concentration of 0.55 mol / L.

[0072] First, add bottom water to the reactor. The volume of bottom water is 0.25 times the volume of the compound metal salt solution. Adjust the pH of the bottom water to 11 using ammonia water. Use deionized water as the bottom water.

[0073] Under stirring conditions at a speed of 700 r / min and a temperature of 50℃, with nitrogen as the protective gas, a compound metal salt solution was added dropwise to the reactor at a rate of 45 mL / min, while a precipitant was added dropwise to control the pH of the material in the reactor to be maintained at 11. After the addition was completed, the reaction was stirred for 10 h.

[0074] Filtration, washing and drying yield the precursor;

[0075] One-time sintering:

[0076] The precursor, LiOH·2H2O, and H3BO3 were mixed in a molar ratio of 1:1.05:0.02, and then added to a ball mill jar. Anhydrous ethanol (35% by weight of the precursor) was added, followed by zirconia grinding beads with a diameter of 0.3 mm. The mixture was then wet-milled for 100 min at a speed of 350 r / min to obtain the ball milling material.

[0077] The precursor has the molecular formula: Ni 0.13 Co 0.13 Mn 0.54 (OH)2;

[0078] In an air atmosphere, the ball mill material was heated to 520°C at a heating rate of 3°C / min, held at that temperature for 4 hours, and then heated to 860°C at a rate of 7°C / min for 9 hours. After cooling, the material was discharged, sieved, and the primary sintered material was obtained.

[0079] Material discreteness:

[0080] The primary sintered material was mixed with anhydrous ethanol at a mass ratio of 4.5:1 and then added to a planetary sand mill. Zirconia grinding beads with a diameter of 0.3 mm were added. The mixture was wet-milled for 55 min at a speed of 960 r / min. During the sand milling process, the material temperature was controlled to not exceed 30℃ by circulating water cooling. After the sand milling was completed, the mixture was rapidly frozen at a temperature of -80℃ for 2 h and then vacuum freeze-dried at a vacuum degree of 0.1 mbar for 24 h to obtain abrasive material with a D50 of 1.5 μm.

[0081] Secondary sintering:

[0082] After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.022, air was introduced at a rate of 0.25 L / min, and the mixture was heated to 1020 °C at a rate of 6 °C / min in the air atmosphere. After sintering at this temperature for 14 h, the mixture was rapidly cooled to room temperature at a rate of 11 °C / min and discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

[0083] Example 3

[0084] The precursor was obtained by co-precipitation:

[0085] A compound metal salt solution was prepared using nickel sulfate, cobalt sulfate, and manganese sulfate as metal salt raw materials, with a Ni:Co:Mn molar ratio of 0.13:0.13:0.54.

[0086] A mixed solution of sodium hydroxide and ammonia was used as the precipitant.

[0087] The precipitant contains sodium hydroxide at a concentration of 4.2 mol / L and ammonia at a concentration of 0.6 mol / L.

[0088] First, add bottom water to the reactor. The volume of the bottom water should be 0.3 times the volume of the compound metal salt solution. Adjust the pH of the bottom water to 11.2 using ammonia water. Use deionized water as the bottom water.

[0089] Under stirring conditions at a speed of 800 r / min and a temperature of 52℃, with nitrogen as the protective gas, a compound metal salt solution was added dropwise to the reactor at a rate of 50 mL / min, while a precipitant was added dropwise to control the pH of the material in the reactor to be maintained at 11.2. After the addition was completed, the reaction was stirred for 12 h.

[0090] Filtration, washing and drying yield the precursor;

[0091] One-time sintering:

[0092] The precursor, LiOH·2H2O, and H3BO3 were mixed in a molar ratio of 1:1.05:0.02, and then added to a ball mill jar. Anhydrous ethanol of 40% of the precursor mass was added, followed by zirconia grinding beads with a diameter of 0.3 mm. The mixture was then wet-milled for 120 min at a speed of 400 r / min to obtain the ball milling material.

[0093] The precursor has the molecular formula: Ni 0.13 Co 0.13 Mn 0.54 (OH)2;

[0094] In an air atmosphere, the ball mill material was heated to 550°C at a heating rate of 4°C / min, held at that temperature for 5 hours, and then heated to 880°C at a rate of 8°C / min for 10 hours. After cooling, the material was discharged, sieved, and the primary sintered material was obtained.

[0095] Material discreteness:

[0096] The primary sintered material was mixed with anhydrous ethanol at a mass ratio of 5:1 and then added to a planetary sand mill. Zirconia grinding beads with a diameter of 0.3 mm were added. The mixture was wet-milled for 60 min at a speed of 1000 r / min. During the sand milling process, the material temperature was controlled to not exceed 30℃ by circulating water cooling. After the sand milling was completed, the mixture was rapidly frozen at a temperature of -80℃ for 2 h and then vacuum freeze-dried at a vacuum degree of 0.1 mbar for 24 h to obtain abrasive material with a D50 of 2 μm.

[0097] Secondary sintering:

[0098] After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.025, air is introduced at a rate of 0.3 L / min, and the mixture is heated to 1050 °C at a rate of 7 °C / min in the air atmosphere. After sintering at this temperature for 15 h, the mixture is rapidly cooled to room temperature at a rate of 12 °C / min and discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

[0099] Example 4

[0100] The difference between this embodiment and Embodiment 1 is as follows:

[0101] During a single sintering process, the heating rate varies, specifically:

[0102] One-time sintering:

[0103] The precursor, LiOH·2H2O, and H3BO3 were mixed in a molar ratio of 1:1.05:0.02, and then added to a ball mill jar. Anhydrous ethanol (30% of the precursor mass) was added, followed by zirconia grinding beads with a diameter of 0.3 mm. The mixture was then wet-milled for 80 min at a speed of 300 r / min to obtain the ball milling material.

[0104] The precursor has the molecular formula: Ni 0.13 Co 0.13 Mn 0.54 (OH)2;

[0105] In an air atmosphere, the ball mill material was heated to 500°C at a heating rate of 6°C / min, held at that temperature for 3 hours, and then heated to 850°C at a rate of 6°C / min for 8 hours. After cooling, the material was discharged, sieved, and the primary sintered material was obtained.

[0106] All other conditions remain unchanged.

[0107] Example 5

[0108] The difference between this embodiment and Embodiment 1 is as follows:

[0109] No ammonia was added to the precipitant, and all other conditions remained unchanged.

[0110] Comparative Example 1

[0111] The difference between this comparative example and Example 1 is that after the first sintering, the material was not dispersed by sand milling and vacuum freeze drying, but was directly subjected to a second sintering, while the other conditions remained unchanged.

[0112] The products obtained from the above embodiments and comparative examples were tested and characterized, and the specific test and characterization results are as follows:

[0113] The particle size distribution range of the products obtained in the examples and comparative examples was tested using a particle size analyzer. The specific test results are as follows:

[0114] Electron micrographs of the products obtained in Example 1 and Comparative Example 1 were observed using SEM. Specific observation results are described in detail below. Figure 1 and Figure 2 Observation reveals that the material obtained by the technical solution in Example 1 has a single crystal morphology and good particle dispersion and uniformity. The product obtained by Comparative Example 1 exhibits an obvious secondary particle morphology and obvious agglomeration.

[0115] The Land battery testing system was used to evaluate the initial capacity performance of the product. The positive electrode formulation was based on a ratio of positive electrode material: conductive agent SuperP: binder PVDF = 8:1:1, with NMP as the solvent. The positive electrode slurry was prepared by stirring using a planetary mixer. Aluminum foil was used as the positive electrode current collector, with a coating thickness controlled at 50 μm and an areal density of 10 mg / cm³. 2 After drying at 80℃ for 12 hours, a 200μm thick lithium sheet was used as the counter electrode. The electrolyte solvent was EC:DMC at a mass ratio of 1:1, with lithium hexafluorophosphate at a concentration of 1mol / L. FEC was added as an additive at a mass fraction of 2%. Using a Celgard 2325 diaphragm, a CR2032 button cell was assembled in an argon glove box with a dew point below -40℃. The electrolyte injection volume was 50μL. After standing and soaking for 12 hours, the cell was charged to a voltage of 4.8V at a current density of 0.05C. After standing for 10 minutes, it was discharged to a cutoff voltage of 2.0V at a discharge current of 0.05C. Based on the discharge capacity and the mass of the active material, the initial discharge capacity was calculated as: initial discharge charge (mAh) / active material mass (g). Detailed calculation results are shown in Table 1.

[0116] Table 1: Product Performance Test Results

[0117]

[0118] As can be seen from the test results in Table 1, the particle size distribution of the product obtained by the present invention is more concentrated, and the initial discharge capacity of the product is also relatively more ideal.

[0119] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a single-crystal lithium-rich manganese-based cathode material, characterized in that, The specific preparation steps include: One-time sintering: The precursor, LiOH·2H2O, and H3BO3 were mixed in a molar ratio of 1:1.05:0.02 and then wet-milled to obtain the ball milling material. The precursor has the molecular formula: Ni 0.13 Co 0.13 Mn 0.54 (OH)2; In an air atmosphere, the ball mill is heated to 500-550℃ at a heating rate of 2-4℃ / min, and then held at that temperature for 3-5 hours. After that, it is heated to 850-880℃ at a heating rate of 6-8℃ / min and held at that temperature for 8-10 hours. After cooling, the material is discharged and sieved to obtain the primary sintered material. Material discreteness: The sintered material was mixed with anhydrous ethanol at a mass ratio of (4-5):1 and then added to a planetary sand mill. Zirconia grinding beads with a diameter of 0.3 mm were added. The mixture was wet-milled for 50-60 minutes at a speed of 900-1000 r / min. During the sand milling process, the material temperature was controlled to not exceed 30℃ by circulating water cooling. After the sand milling was completed, the mixture was freeze-dried to obtain abrasive material with a D50 of 1-2 μm. The freeze-drying includes: After being rapidly frozen at -80℃ for 2 hours, it was then freeze-dried under vacuum at a vacuum degree of 0.1 mbar for 24 hours. Secondary sintering: After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.02-0.025, the mixture is heated to 1000-1050℃ in air and sintered for 12-15 hours. After cooling, the material is discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

2. The method for preparing a single-crystal lithium-rich manganese-based cathode material according to claim 1, characterized in that, The specific preparation steps of the precursor include: The precursor was obtained by co-precipitation: A composite metal salt solution was prepared with a Ni:Co:Mn molar ratio of 0.13:0.13:0.

54. A mixed solution of sodium hydroxide and ammonia was used as the precipitant. First, add bottom water to the reactor. The volume of bottom water should be 0.2-0.3 times the volume of the compound metal salt solution. Adjust the pH of the bottom water to 10.8-11.2 using ammonia. Under stirring, nitrogen was used as a protective gas. Then, a compound metal salt solution was added dropwise to the reactor at a uniform rate, and a precipitant was added dropwise at the same time to control the pH of the material in the reactor to be maintained at 10.8-11.

2. After the addition was completed, the reaction was stirred for 8-12 hours. The precursor is obtained by filtration, washing, and drying.

3. The method for preparing a single-crystal lithium-rich manganese-based cathode material according to claim 1, characterized in that, The wet ball milling includes: Add the material to the ball mill jar, and add anhydrous ethanol at 30-40% of the mass of the precursor. Then add zirconia ball milling beads with a diameter of 0.3 mm, and ball mill and mix for 80-120 min at a speed of 300-400 r / min.

4. The method for preparing a single-crystal lithium-rich manganese-based cathode material according to claim 1, characterized in that, The secondary sintering also includes: After mixing abrasive sand and lithium carbonate at a mass ratio of 1:0.02-0.025, air is introduced at a rate of 0.2-0.3 L / min, and the mixture is heated to 1000-1050℃ at a rate of 5-7℃ / min in the air atmosphere. After sintering at this temperature for 12-15 hours, the mixture is rapidly cooled to room temperature at a rate of 10-12℃ / min and discharged to obtain a single-crystal lithium-rich manganese-based cathode material.

5. The method for preparing a single-crystal lithium-rich manganese-based cathode material according to claim 2, characterized in that, The precipitant contains sodium hydroxide at a concentration of 4.0-4.2 mol / L and ammonia at a concentration of 0.5-0.6 mol / L.

6. The method for preparing a single-crystal lithium-rich manganese-based cathode material according to claim 2, characterized in that, The precursor obtained by co-precipitation also includes: Under stirring conditions at a speed of 600-800 r / min and a temperature of 48-52℃, with nitrogen as the protective gas, a compound metal salt solution is added dropwise to the reactor at a rate of 40-50 mL / min, while a precipitant is added dropwise to adjust the pH of the material in the reactor to be maintained at 10.8-11.

2. After the addition is completed, the reaction is stirred for 8-12 hours.

7. A single-crystal lithium-rich manganese-based cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

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